Is it easier/more cost effective to assemble your own upper than buy a completed one?

Instead of waiting 6 months or paying $1000 for my upper, could I instead put on together piece by piece? I've never done this before so I'm not sure if any parts will fit with any upper or even really what all I need. So far on my list from what I've found are:

easier yes, more cost effective.... well not any more, but if you can find cheap used parts it can work out ok. (you really need a master smith to put it all together though).... and Randall isn't doing mixmatch builds anymore... (apparently all the ones I had him do burned him out on it)

You used to be able to get a complete m16A1 pencil barreled surplus upper for $310 (I bought two at that price back in 2006-2007)

I'm in the same boat as you and my conclusion has been to buy it fully assembled, at least the first time. The main reason behind this decision is the fact that you need to adjust the bolt carrier group and barrel such that there is proper "headspace" (wikipedia it). With improper headspace it could lead to catostophic failure of the rifle (basically exploding) which as you can imagine could lead to death, loss of limbs or just a fubar rifle if you're lucky. Is getting proper headspace fairly easy to do? Maybe, I'm not sure. Would I bet my life that I did it right with little to no experience? No way.

I'm in the same boat as you and my conclusion has been to buy it fully assembled, at least the first time. The main reason behind this decision is the fact that you need to adjust the bolt carrier group and barrel such that there is proper "headspace" (wikipedia it). With improper headspace it could lead to catostophic failure of the rifle (basically exploding) which as you can imagine could lead to death, loss of limbs or just a fubar rifle if you're lucky. Is getting proper headspace fairly easy to do? Maybe, I'm not sure. Would I bet my life that I did it right with little to no experience? No way.

There is no headspace to adjust; barrels come as an assembly with the barrel extension already headspaced to the barrel and installed. Unless you get one that is horribly assembled, you shouldn't have a problem. I've built dozens of AR type rifles and never encountered one that was so improperly assembled that it was dangerous.

I was not aware of that. I heard about the headspace danger from other AR-15 enthusiasts, who admitantly never built thier own upper assembly.

However, I watched the Brownells AR-15 assembly videos online (free and highly reccomended) and during the barrel assembly portion he mentioned the headspace issue and talked about possible death if done improperly, further reinforcing what I had heard earlier. He did however have a no-go headspace tool to make sure the bolt wouldn't lock with it in. Incidentally I heard you should have a "go" headspace tool as well which he did not use AFAIK.